Towards high-bandwidth organic photodetection based on pure active layer polarization

Abstract

Organic photodetectors offer distinct advantages over their inorganic analogues, most notably through optical transparency and flexibility, yet their figures-of-merit still lag behind those of inorganic devices, and optimization strategies generally encounter a trade-off between device responsivity and bandwidth. Here we propose a novel photodetector architecture in which an organic photoactive semiconductor layer (S) is sandwiched between two thick insulating layers (I) that separate the semiconductor from the metallic contacts (M). In this architecture a differential photocurrent response is generated purely from the polarization of the active layer under illumination. Especially for an asymmetric MISIM design, where one insulating layer is a high-k ionic liquid IIL and the other a low-k polymer dielectric Ip, the responsivity/bandwidth trade-off is broken, since the role of the IIL in efficient charge separation is maintained, while the total device capacitance is reduced according to Ip. Thus the benefits of single insulating layer differential photodetectors (MISM) using either IIL or Ip are combined in a single device. Further improvements in device performance are also demonstrated by decreasing the series resistance of the photoactive layer through semiconductor:metal blending and by operation under strong background light.

Pulsed‐Laser Detectors Based on Metal Halide Perovskites

“…We attributed this phenomenon to the polarization effect, which has been reported in other optoelectronic conversion systems. [ 30–35 ] The photogenerated carriers can be accumulated on two electrodes and form photovoltage simultaneously, and the photovoltage can further polarize the PVDF interlayer slowly. When the light switched off, photovoltage of the conventional photodiodes vanished immediate, which is mainly determined by the charge carrier lifetime within the devices.…”

Potential modulations in flatland: near-infrared sensitization of MoS2 phototransistors by a solvatochromic dye directly tethered to sulfur vacancies

“…Action spectra measurements were performed by a lock-in method at 263 Hz, as reported previously 33 over a wavelength range 350–1700 nm, as further described in the ESI. Phototransistor characterization (Keithley 2636B/LabVIEW) was performed in the dark or under illumination from a fibre-coupled LED ( λ max = 640 nm or 1310 nm, P max = 260 μWcm −2 set for both).…”

Stabilization of Interfacial Polarization and Induction of Polarization Hysteresis in Organic MISIM Devices

“…When the field is reduced to zero, this type of polarization disappears due to charge recombination in most cases, but there are a few examples in which polarization is retained by some trapping mechanisms of the surface charges. , To stabilize the interfacial polarization, we propose the metal|insulator|semiconductor|insulator|metal (MISIM) structure (Figure ). In our previous works, we examined organic photocells with this MISIM structure, , which can effectively convert modulated light to polarization current (Figure S1). In MISIM photocells, the electrical polarization in the I layer enhances the photoinduced charge separation in the S layer and traps the photogenerated carriers at the I/S interfaces.…”

“…16,17 To stabilize the interfacial polarization, we propose the metal|insulator|semiconductor|insulator|metal (MISIM) structure (Figure 1). In our previous works, we examined organic photocells with this MISIM structure, 18,19 which can effectively convert modulated light to polarization current (Figure S1). In MISIM photocells, the electrical polarization in the I layer enhances the photoinduced charge separation in the S layer and traps the photogenerated carriers at the I/S interfaces.…”